U.S. Pat. No. 4,652,748 discloses an angle step indicator. It consists of a housing in which a hollow shaft is rotatably seated. A coding disk for measuring the angular position of the shaft with respect to a scanning unit fastened to the housing is fastened on this shaft, fixed against relative rotation. One end of the shaft is slitted and has a conical interior bore on which the conical tip of a pin acts. The pin is axially displaceable by a screw inserted into the other end of the shaft so that the slitted end of the shaft is spread open. The shaft of the angle measuring system is radially clamped by this spreading open of the slitted end of the shaft in either a bore of an element of a shaft coupling or directly in a bore of a motor shaft. In every case the shaft of the angle measuring device is connected with the driveshaft, for example a motor shaft, by a shaft coupling.
A similar angle measuring device is described in German Patent Publication No. DE 30 38 005 A1. In this example the shaft end facing the drive unit is also slitted. This shaft end can be spread open by a wedge. The wedge has an interior thread which works together with the exterior thread of a screw. The head of the screw is supported on the shaft end, so that the screw itself is not axially displaceable. The thread flanks of the screw are displaced in the axial direction by turning the screw, which causes an axial displacement of the wedge and thus radial spreading of the slitted shaft end.
All known measuring systems have the disadvantage that, in addition to the screw, other elements, are still required for spreading.
It is thus desirable to provide an angle measuring system with a clampable shaft with relatively fewer elements then known systems and which is simple to implement.